The correct answer is (c) FTP.
FTP (File Transfer Protocol) is a standard network protocol used to transfer files from one computer to another over a TCP/IP network. It is a client-server protocol, which means that there is a server that stores the files and a client that requests the files. The client connects to the server using the FTP protocol and then requests the files that it wants to download. The server then sends the files to the client.
TCP/IP (Transmission Control Protocol/Internet Protocol) is a set of protocols that allow computers to communicate with each other over a network. It is the most common protocol used on the Internet. SMTP (Simple Mail Transfer Protocol) is a protocol used to send email messages over a network.
(a) TCP/IP is a protocol that allows computers to communicate with each other over a network. It is not a protocol specifically used for file transfer.
(b) SMTP is a protocol used to send email messages over a network. It is not a protocol specifically used for file transfer.
(d) All of these is not the correct answer because only (c) FTP is a protocol specifically used for file transfer.